This invention relates to the preparation of unsaturated esters by the catalyzed oxyacylation reaction of C.sub.3 or higher olefins, oxygen and a carboxylic acid in the vapor phase.
The preparation of alkenyl esters by the vapor phase reaction of olefins, carboxylic acids and oxygen in the presence of noble metal containing catalysts, especially palladium, is well-known. Thus, when using ethylene, vinyl acetate is obtained, and when using propylene, allyl acetate is prepared. U.S. Pat. No. 3,190,912 granted to Robinson discloses such a reaction and is hereby incorporated by reference.
Over the years, the noble metal catalyzed reaction has been constantly improved because, for one reason, the noble metal catalyst is very expensive and is an important cost factor in the process. In U.S. Pat. No. 3,627,821 the reaction is carried out with a catlyst containing palladium acetate, alkali metal acetate and one or more uranium compounds, said catalyst having improved lifetime and space/time yields. U.S. Pat. No. 3,670,014 uses bismuth in combination with palladium to increase the space/time yields when propylene is the olefin. Lead metal is disclosed as useful in combination with palladium in U.S. Pat. No. 3,917,676 and antimony is used with palladium in U.S. Pat. No. 4,016,200. Improving the process has also resulted in modifications to the palladium containing carrier as shown, for example, in U.S. Pat. No. 3,939,199 wherein the carrier is silicic acid having a special pore volume and pore diameter. It has now been found that C.sub.3 or higher olefins may be oxyacylated in the vapor phase to form unsaturated esters without the need for a noble metal catalyst.
It is an object of this invention to provide an improved oxyacylation process for the preparation of unsaturated esters from C.sub.3 or higher olefins. Other objects and advantages will become apparent from the following description.